JPH07134427A - Electrophotographic photoreceptor and electrophotographic device - Google Patents

Abstract

PURPOSE:To provide an electrophotographic photoreceptor which is excellently durable in direct electrification, and an electrophotographic device equipped with it. CONSTITUTION:In the electrophotographic photoreceptor 1, which is directly electrified at least and has photosensitive layers 3 and 4 formed on its cylindrical substrate 2 by dip coating, at least one of the ends of the substrate 2 is larger in outside diameter than its other parts and the larger-diameter end also has the photosensitive layers 3 and 4 which continue to the other parts, and the electrophotographic device is equipped with the electrophotographic photoreceptor 1. Thus, the electrophotographic photoreceptor excellent in durability and productivity and the electrophotographic device provided with this can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member which can be widely used in electrophotographic application fields using direct charging, such as an electrophotographic apparatus, a laser beam printer, and a plain paper FAX, and an electrophotographic apparatus having the same. Regarding

[0002]

BACKGROUND OF THE INVENTION Electrophotographic photoreceptors are generally constructed by providing a photoconductor coating on a cylindrical substrate. As a method for forming the film, there are methods such as coating, vapor deposition, and CVD.
Of these, dip coating is most often used.

In dip coating, there is a so-called sagging phenomenon in which the thickness of the coating film gradually increases with time compared to the time when the substrate is pulled up from the coating tank. Therefore, various studies have been attempted in order to cope with this and obtain the film thickness uniformity in a wider region in the lengthwise direction of the photoconductor. However, in the dip coating, sagging cannot be essentially avoided, and reducing sagging conflicts with productivity, so that a compromise is made at a certain level.

On the other hand, as a charging device used in an electrophotographic apparatus, a corona discharge device has been generally used. However, these days, the direct charging device for bringing a roller-type or blade-type conductive member into contact with the photoconductor has the advantages that the power supply can be reduced in voltage and that the generation of ozone is extremely small. It is being adopted.

In such direct charging, an AC voltage is applied by superimposing it on a DC voltage for uniform charging. At this time, there is a phenomenon that the polymer forming the photosensitive layer is decomposed by Joule heat of a current flowing from the charging member to the photosensitive member during charging and is easily worn.

Therefore, in the direct charging process, the required film thickness of the photosensitive layer is unavoidably increased, which results in a large sag value.

Further, in order to reduce the size of the electrophotographic apparatus,
It is necessary to shorten the length of the photoconductor, which inevitably causes the charging member to come into contact with the sagging portion where the film thickness is thin, but since the film thickness is thin in the center part, the capacity is large. Since the impedance is small, more current flows and wear is promoted. That is, there is a problem that the life of the photoconductor is significantly limited because the amount of wear at the place where the film thickness is originally small is further increased.

Further, as the process speed of the electrophotographic apparatus increases, the current flowing through the photoconductor becomes larger and the amount of abrasion of the film also becomes larger.

As described above, in the direct charging process, it is necessary to further suppress the film thickness sag of the photoconductor, which has not been a problem in the conventional corona charging process. It is becoming more severe in the trend of increasing speed and processing speed.

[0010]

SUMMARY OF THE INVENTION The present invention prevents an abnormal wear of a photoconductor caused by the direct charging as described above, and has an electrophotographic photoconductor having a photosensitive layer with a very small sag, that is, a uniform film thickness. And an electrophotographic apparatus having the same.

[0011]

That is, the present invention relates to an electrophotographic photosensitive member to which at least direct charging is applied, wherein the photosensitive layer is formed by dip coating on a cylindrical substrate, At least one end portion of the base is formed to have a larger outer diameter than the other portions,
In addition, the electrophotographic photosensitive member is characterized in that the photosensitive layer is continuously formed on the other portion even at the end having a large outer diameter.

The present invention is also an electrophotographic apparatus comprising the above electrophotographic photosensitive member.

The present invention will be described in detail below.

As means for suppressing the film thickness sagging in the dip coating, one of the methods is to increase the viscosity of the coating liquid and decrease the coating rising speed. However, this method is not preferable because the productivity is significantly reduced.

On the other hand, a method has also been proposed in which a dummy member is mounted on the substrate to be coated and the dip coating is started from there to flatten the film thickness of the coating region of the photoconductor to be actually used. However, even with this method, a decrease in productivity cannot be avoided.

On the other hand, the present invention provides a step on the upper part of the substrate from the beginning. As a means for this, when the substrate of the photoconductor is a metal such as aluminum, a step can be easily provided by partially modifying the conditions of the cutting process that is generally performed to obtain accuracy. If the substrate is resin, this can be easily dealt with by changing the molding die.

The size of the step with respect to the diameter of the central portion is preferably 0.01 to 2.0 mm, and 0.02 to 1.
0 mm is more preferable. If it is less than 0.01 mm, the effect of the present invention is not sufficient. On the other hand, if it is larger than 2.0 mm, bubbles are entrained during the immersion and the film thickness is disturbed, which is not preferable.

The photosensitive layer provided on the substrate is provided by dip coating. There are no particular restrictions on the materials and solvents used.

The layer structure of the photosensitive layer is generally a laminate of a charge generation layer and a charge transport layer. In this case,
The subject of the invention is in particular the charge transport layer.

FIG. 1 illustrates a specific embodiment of the present invention.
In FIG. 1A, 1 is a photoconductor, 2 is a cylindrical substrate, and a step is provided on one side. Reference numeral 3 is a charge generation layer, and 4 is a charge transport layer, which is also applied to the end portion beyond the step. Reference numeral 5 denotes a direct charging member that is brought into contact with the photosensitive member, and here, a roller-shaped member is shown. For comparison, FIG. 1 (b) shows a substrate having no step.

FIG. 2 shows a schematic structural example of a transfer type electrophotographic apparatus using the electrophotographic photosensitive member of the present invention.

In the figure, 101 is a drum type photosensitive member of the present invention as an image bearing member, which is rotationally driven around a shaft 101a in a direction of an arrow at a predetermined peripheral speed. The photosensitive member 101 receives a uniform charge of a predetermined positive or negative potential on its peripheral surface by a charging means 102 during its rotation process, and then the exposure unit 103.
Then, an optical image exposure L (slit exposure, laser beam scanning exposure, etc.) is received by an image exposing means (not shown). As a result, electrostatic latent images corresponding to the exposed image are sequentially formed on the peripheral surface of the photoconductor.

The electrostatic latent image is then toner-developed by the developing means 104, and the toner-developed image is transferred by the transfer means 105 from the paper feed unit (not shown) to the rotation of the photosensitive body 101 between the photosensitive body 101 and the transfer means 105. The images are sequentially transferred onto the surface of the transfer material P that is synchronously taken out and fed.

The transfer material P, which has received the image transfer, is separated from the surface of the photoconductor and introduced into the image fixing means 108 to undergo the image fixing and printed out as a copy.

After the image transfer, the surface of the photoconductor 101 is cleaned by the cleaning means 106 to remove the residual toner after transfer, and is further discharged by the pre-exposure means 107 to be repeatedly used for image formation.

A direct charging device is used as the uniform charging means 102 of the photosensitive member 101. The electrophotographic apparatus is configured by integrally combining a plurality of constituent elements such as the photoconductor, the developing unit, and the cleaning unit described above as an apparatus unit, and the unit is configured to be detachable from the apparatus body. May be. For example, the photosensitive member 101 and the cleaning means 106 may be integrated into one device unit, and the device body may be detachably configured by using a guide means such as a rail. At this time, the above device unit may be provided with a charging unit and / or a developing unit.

When the electrophotographic apparatus is used as a copying machine or a printer, the optical image exposure L is reflected light or transmitted light from a document, or the document is read and converted into a signal, and a laser beam is scanned based on this signal. Or driving an LED array or a liquid crystal shutter array.

When the electrophotographic apparatus of the present invention is used as a printer for a facsimile, the light image exposure L becomes an exposure for printing received data. FIG. 3 is a block diagram showing an example of this case.

The controller 111 controls the image reading section 110 and the printer 119. The entire controller 111 is controlled by the CPU 117. Image reading unit 1
The read data from 10 is transmitted to the partner station via the transmission circuit 113. The data received from the other station is the receiving circuit 1
12 to the printer 119. The image memory 116 stores predetermined image data. The printer controller 118 controls the printer 119.
114 is a telephone.

The image information received from the line 115 (image information from a remote terminal connected through the line) is
After being demodulated by the receiving circuit 112, a decoding process is performed by the CPU 117 and sequentially stored in the image memory 116. When the image information of at least one page is stored in the memory 116, the image recording of that page is performed. CPU11
Reference numeral 7 reads the image information of one page from the memory 116 and sends the decoded image information of one page to the printer controller 118. Printer controller 118
When the image information of one page is received from the CPU 117, the printer 1
Control 19.

The CPU 117 is receiving the next page while the printer 119 is recording.

The image is received and recorded as described above.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines but also in laser beam printers, C
RT printer, LED printer, liquid crystal printer,
It can be widely used in electrophotographic application fields such as laser plate making.

[0034]

EXAMPLES Next, the present invention will be described with reference to examples. [Example 1] As a substrate, an aluminum cylinder raw tube having a diameter of 30 mm, a diameter of 254 mm, and a thickness of 0.9 mm was prepared. This was subjected to outer diameter cutting to a wall thickness of 0.7 mm and a surface roughness of 2S. However, one end of the cylinder end having an upper end of 5 mm was not cut, and a step of 0.2 mm was formed.

With the stepped portion of this substrate facing upward, layers having the following constitution were sequentially laminated by dip coating to prepare a photoreceptor.

(1) Conductive coating layer: Mainly composed of tin oxide and titanium oxide powder dispersed in a phenol resin. Film thickness 15 μm. (2) Undercoat layer: Mainly composed of modified nylon and copolymer nylon. The film thickness is 0.6 μm. (3) Charge generation layer: Mainly composed of a phthalocyanine pigment having absorption in a long wavelength region dispersed in butyral resin.
The film thickness is 0.2 μm. These layers are 6 mm from the top of the substrate
The dip coating was started from the position. On the other hand, (4) the charge transport layer was applied by dip coating from a position 2 mm from the upper end of the substrate. The composition of the coating liquid and the coating conditions are as follows.

[0037] Charge transport material (CTM): Hole transport hydrazone compound Binder: Polycarbonate Z resin (M _V = 200
00) ・ CTM / binder ratio: 8/10 ・ Solvent: chlorobenzene / dichloromethane = 4/1 ・ Solid content: 21% ・ Viscosity: 120 mPas ・ Coating speed: 300 mm / sec ・ Film thickness (of the rising part): 25 μm

The thus prepared photoconductor was mounted on a laser beam printer (manufactured by Canon, which was modified so that 16 sheets could be printed per minute based on LBP-EX), and a durability test was conducted.

[Comparative Example 1] An aluminum cylinder was cut on the entire surface to prepare a substrate having no step, and a photosensitive layer was provided thereon in the same manner as in Example 1 to prepare a photoreceptor.

A durability test was conducted on this photosensitive member in the same manner as in Example 1. The results are shown in Table 1.

The printer used here is of a direct charging type, and the charging member has a structure in which a conductive rubber roller is pressed against the drum. This charging roller has a length of 225 mm
Then, the upper side of the coating of the photoconductor is in contact with a position 13.5 mm from the end, and the lower side is in contact with a position of 15.5 mm from the end.

Therefore, the film thickness of the photosensitive member (the film thickness of the charge transport layer) at the position where the end portion of the charging roller contacts and the central portion was measured. The results are also shown in Table 1.

As is clear from these results, the photoreceptor of the present invention has satisfactory durability because the film thickness on the upper end side of the coating is sufficiently thick, but the photoreceptor of Comparative Example 1 is coated. Since the film thickness on the upper end side is thin, the abrasion caused between the charging member and the charging member, resulting in an image of defective charging.

[Example 2] In the above electrophotographic printer, the same test as in Example 1 was conducted by replacing the charging member with a conductive rubber blade. The results are shown in Table 1.

The length of the charging blade and the contact position with respect to the photosensitive member are the same as in the first embodiment.

[Embodiment 3] As a base material, a resin in which a conductive filler is mixed to give conductivity is used.
It was molded into the same size as the substrate used in. However, the wall thickness is 2
mm. A photosensitive layer was applied to this substrate in the same manner as in Example 1 to prepare a photosensitive member.

[Embodiment 4] The aluminum tube used in Embodiment 1 was cut to an outer diameter to have a wall thickness of 0.7 mm and a surface roughness of 2S. However, one of the upper ends of the cylinder end 5
The thickness of mm is 0.8 mm and 0.1 mm
Formed a step. The same photosensitive layer as in Example 1 was formed on this by dip coating. However, the charge transport layer was applied under the following conditions.

CTM: hole transporting stilbene compound Binder: polycarbonate Z resin (M _V = 400)
00) -CTM / binder ratio: 10 / 10-Solvent: Chlorobenzene / Tetrahydrofuran = 1 / 1-Solid content: 20% -Viscosity: 220 mPas-Coating speed: 270 mm / sec-Film thickness (of the rising part): 25 μm A durability test was conducted on these photoreceptors in the same manner as in Example 1. The results are shown in Table 1.

In all the examples, the effects of the present invention are sufficiently obtained.

[0050]

[0051]

As described above, it is understood that the photoconductor of the present invention is suitable for the direct charging system. In addition, it greatly contributes to speeding up and image quality improvement of the electrophotographic apparatus using direct charging.

[Brief description of drawings]

FIG. 1 is a schematic view of a contact state between a photosensitive member and a charging member.

FIG. 2 is a schematic configuration diagram of a transfer type electrophotographic apparatus of the present invention.

FIG. 3 is a block diagram of a facsimile using the electrophotographic apparatus as a printer.

Claims (2)

[Claims] 1. An electrophotographic photosensitive member to which at least direct charging is applied, wherein a photosensitive layer is formed on a cylindrical substrate by dip coating, and at least one end of the substrate is An electrophotographic photosensitive member having an outer diameter larger than that of other portions, and having a photosensitive layer continuously formed on the end portion having a larger outer diameter in the other portions. 2. An electrophotographic apparatus comprising the electrophotographic photosensitive member according to claim 1.